1. Field of the Invention
The present invention relates to a rare earth magnet having high electric resistance, and in particular, relates to a rare earth magnet with high electric resistance to be used in a motor for electronic equipment and automobile driving.
2. Description of Related Art
An inexpensive ferritemagnet has conventionally been used widely as a magnet for a permanent magnet type motor. However, use of a rare earth magnet with higher performance has been increasing year by year with demand for development of more compact rotating electrical appliances with higher performance. Development of a rare earth magnet, represented by Sm—Co type magnet and Nd—Fe—B type magnet, is under way, aiming at higher performance and lower price. A rare earth magnet, however, has low electric resistance because it is a metal magnet, leading to a problem of lowering a motor efficiency due to increased eddy-current loss when built in a motor. Therefore, various technologies have been proposed to solve the above problem by forming structure with insulating material inserted inside the rare earth magnet to increase electric resistance of a molded rare earth magnet itself.
For example, a rare earth magnet, wherein magnetic powder for rare earth magnet is bound by SiO2 and/or Al2O3 particles, is proposed (see JP-A-10-321427). A method for producing a rare earth magnet is also disclosed, where M(OH)n coated powder composed of sol liquid of a metal alkoxide hydrolyzate, M(OH)n (M is one or more kinds of metal elements such as Si, Zr, Ti, Al, Cr, Ce, Co and Y; n is valence of M) and rare earth-iron type magnet particles are heated under compression, and these powder are fixed by electrical heating and compression using pulsed current while forming an amorphous metal oxide layer (MO(n/2)) at the boundary of the rare earth-iron type magnet particles, and (see JP-A-6-69009).